Studies were continued on the efflux of cholesterol from human skin fibroblasts. Cells were initially grown in protein- and lipid-free medium and their cholesterol content raised by incubation with low density lipoproteins (LDL). A subsequent incubation with a high density lipoprotein fraction with HDL 3 (d. 1.125-1.21), but not with HDL 2 (d. 1.063-1.125), reduced within 24 hr the cell cholesterol content by 14% compared with an incubation without lipoproteins. Plasma d. 1.21 infranatant proteins were substantially less effective than HDL (d. 1.063-1.21) or VHDL (d. 1.21-1.25). Effects on sterol synthesis paralleled the effects on cholesterol content. The percent of esterified sterol in total cholesterol did not change greatly on incubation with HDL, but some data were consistent with a primary egress of free cholesterol and a simultaneous slow hydrolysis of cholesterol esters. The results suggest a slow efflux of cholesterol from normal fibroblasts with its rate determining indirectly the rate of uptake and the content of cholesterol at a steady-state equilibrium.